Tuesday

November 25, 2014

November 25, 2014

Total # Posts: 4,077

**Chemistry**

If the standard enthalpy of formation of PH3(g) is +5.4 kJ mol-1, calculate the reaction enthalpy for 2PH3(g)--->2P(s)+3H2(g)
*October 20, 2012*

**Chemistry**

When 10.0 g of ammonium nitrate (molar mass= 80 g/mol) are dissolved in 1.00 L of water in a bomb calorimeter with a heat capacity of 2.30 kJ/ K, the temp drops 1.52 K. What is the molar enthalpy of solution of ammonium nitrate?
*October 20, 2012*

**Chemistry**

The standard enthalphies of formation of ozone, O3(g), and oxygen atoms are +142.70 and +249.17 kJ/mol. Calculate the reaction enthalpy for 2O2(g)-->O3(g)+O(g)
*October 20, 2012*

**PHI 103 Informal Logic**

4. After being told that she is being punished for lying, a child responds by telling her mother that she also lied. This response may involve which fallacy? (Points : 1) Ad homimen (tu quoque) Ad verecundiam (ex libris) Ad misericordiam (ex ante) Ad baculum (antebellum
*October 20, 2012*

**Chemistry**

How many mL of 0.200 M H3PO4(aq) must be added to 25.0 mL of 0.0888 M BaCl2(aq) to precipitate all the barium as barium phosphate?
*October 20, 2012*

**Chemistry**

Calculate the number fo moles of NaOH(aq) needed to react completely with 125 mL fo 6.00 M H2SO4(aq)
*October 20, 2012*

**Chemistry**

**SNO2(s)
*October 20, 2012*

**Chemistry**

Please show me how to work! thanks When Snno2(s) is formed form the comustion of gray tin, the reaction enthalpy is -578.6 kJ, and when white tin is burned to form SnO2(s), the reaction enthalpy is -580.7 kJ. Calculate the reaction enthalpu for Sn(gray)-->Sn(white)
*October 20, 2012*

**Chemistry**

Please show me how to work! Ethane, C2H6(g) can be made by reaction of hydrogen gas with acetylene, C2H2(g). the standard enthalpies of formation of ethane and acetylene are -84.68 and +226.73 kJ mol-1, respectively. what is the reaction enthalpy for the production of one mole...
*October 20, 2012*

**Chemistry**

If the standard enthalpy of combustion of octane, C8H18(l) is -5471 kJ/mol, calculate the enthalpy change when 1.00 kg of octane are burned. the molar mass of octane is 114 g/mol
*October 20, 2012*

**Gen Chem**

Ethane, C2H6(g) can be made by reaction of hydrogen gas with acetylene, C2H2(g). the standard enthalpies of formation of ethane and acetylene are -84.68 and +226.73 kJ mol-1, respectively. what is the reaction enthalpy for the production of one mole of ethane? Write the ...
*October 20, 2012*

**Gen Chem**

If the standard enthalpy of combustion of octane, C8H18(l) is -5471 kJ/mol, calculate the enthalpy change when 1.00 kg of octane are burned. the molar mass of octane is 114 g/mol
*October 20, 2012*

**Math**

I got a magnitude of 6.1. Is that correct?
*October 20, 2012*

**Math**

What magnitude of earthquake would release energy equivalent to 35 trillion jules? I know the formula is: E= (2.5 X 10^4) X 10^1.5 X M
*October 20, 2012*

**ap chemistry :(**

consider the reaction C6H14 + 9.5O2 yields 6CO2 + 7H2O at constant pressure. which response is true? 1. work may be done on or by the system as the reaction occurs, depending upon the temperature. 2. work is done on the system as the reaction occurs. 3. no work is done as the ...
*October 18, 2012*

**Force Physics**

A block with a mass of 12 kg and a sphere with a mass of 10 kg is suspended by two spring scales. What is the reading on the top and bottom scale?
*October 18, 2012*

**math s**

Solve 16x – 15 = –5x + 48
*October 17, 2012*

**math**

7 – 4(x + y) + 2(x – 3y) A 7 – 2x – 7y B.7 – 2x – 10y(*) C.7 + 2x – 7y d.7 + 2x – 10y i think its be im not aure can some one check my ansswer
*October 17, 2012*

**Pre-Algerbra**

quadrantlll (-2,-4)
*October 17, 2012*

**Math**

If the pH of a solution increases by 4 (from 4 to 8), how much does the hydrogen ion concentration change? Does the change make the solution more acidic or more basic?
*October 17, 2012*

**history**

Loyalists believed Patriots were breaking the law. should return to England. should support British taxation. were too aristocratic. i think its c im not sure
*October 16, 2012*

**history**

i got b is that right
*October 16, 2012*

**Math**

My median answer is 19 for the ages of houses. How do I explain this represents the ages of the houses best? having trouble wiht explaining it.
*October 16, 2012*

**Physics**

A surfer is catching a wave. Suppose she starts at the top of the wave with a speed of 1.3 m/s and moves down the wave until her speed increases to 8.0 m/s. The drop in her vertical height is 2.8 m. If her mass is 59 kg, how much work is done by the (nonconservative) force of ...
*October 15, 2012*

**Physics**

A 1600-kg car experiences a combined force of air resistance and friction that has the same magnitude whether the car goes up or down a hill at 32 m/s. Going up a hill, the car's engine produces 54 hp more power to sustain the constant velocity than it does going down the ...
*October 15, 2012*

**College Chem**

The density of the Earth is about 3.5g/cubic centimeters. If the Earth has a radius of 1.126 by 10 (to the seventh power) meters, what is its mass? (hint: volume= 4(pie)r(to the third power)/3; 1 meter=100 centimeters
*October 14, 2012*

**Chemistry**

Calculate the entropy change when 2.42 g of H2 reacts with O2 according to the reaction 2 H2(g) + O2(g) → 2 H2O(ℓ) at 298 K and 1 atm pressure. The standard molar enthalpy of formation of H2O(ℓ) at 298 K is −285.8 kJ/mol. The corresponding free energy ...
*October 14, 2012*

**Physics**

Block A and Block B in the figure below are connected by a string of negligible mass. There is a force on A with a magnitude of FA=20N and a force on B with a magnitude FB=34N in the directions shown in the figure. What is the tension in the string?
*October 14, 2012*

**Math**

How did you get that?
*October 14, 2012*

**Math**

The doubling time of a city's population is 17 years. How long does it take for the population to quadruple?
*October 14, 2012*

**Logarithms**

Ok thanks
*October 14, 2012*

**Logarithms**

if log base 10 of 2 = .301 then what is log base of 10 of 2000? I know how to solve with a calculator but I'm having a hard time doing it without one.
*October 14, 2012*

**Logarithms**

It's fine. Thanks
*October 14, 2012*

**Logarithms**

Yes Damon thats what I meant. Thanks!
*October 14, 2012*

**Logarithms**

Using the approximation log10^2=0.301, find: log10^8
*October 14, 2012*

**Chemistry**

A gas-phase reaction has Kp = 2.44 × 10 20 at 25 ◦ C. Calculate ∆G 0 for this reaction. Answer in units of kJ/mol rxn
*October 14, 2012*

**Chemistry**

The standard molar Gibbs free energy of formation of NO2 (g) at 298 K is 51.30 kJ · mol −1 and that of N2O4 (g) is 97.82 kJ · mol −1 . What is the equilibrium constant at 25 ◦ C for the reaction 2 NO2(g) <=> N2O4(g) ?
*October 14, 2012*

**Physics**

When a spacecraft travels from the Earth to the Moon, both the Earth and the Moon exert a gravitational force on the spacecraft. Eventually, the spacecraft reaches a point where the Moon's gravitational attraction overcomes the Earth's gravity. How far from the Earth&#...
*October 13, 2012*

**stats**

blood cholesterol level of all men age 20-24 follows N(188,41) where the units for the men and standard deviation are in mg/dl. what is the probability that the sample mean takes a value between 185 and 191 if we sample 1000 men
*October 12, 2012*

**Science**

When a car slams on its brakes what provides friction that helps the car stop? What kind of energy is produced?
*October 11, 2012*

**Maths Percentage (6th Grade)**

David has $5 in his wallet. This was 10% of the amount that he received from his mother. Find the total amount of money that David received from his mother. 35% of the number of books Ibrahim owns are fiction boos, find: a.) the total number of books he owns. b.) the number of...
*October 11, 2012*

**Math**

ok stuck again. Got everything else calculated, but why is the median the best choice? is it because 19 is the closest to the mean, 16.75 ? Can you explain??
*October 10, 2012*

**pre-ap Algebra 2**

write a polynomial function f of least degree that has the rational coefficients, a leading coefficient of 1, and the given zeros. Given zeros: -2,2,-1,3, sqrt 11
*October 10, 2012*

**physics**

Two mountain climbers are working their way up a glacier when one falls into a crevasse. The icy slope can be considered frictionless. Sue's (the one who fell) weight is pulling Paul up the 45 degree slope. If Sue's mass is 66 kg and if she falls 2 min 10 s (starting ...
*October 9, 2012*

**Integrated 2**

Aaron has 20 dimes and nickels which together total is 1.40 how many of each does he have
*October 9, 2012*

**Physics**

Two pole-vaulters just clear the bar at the same height. The first lands at a speed of 8.50 m/s, and the second lands at a speed of 8.80 m/s. The first vaulter clears the bar at a speed of 1.50 m/s. Ignore air resistance and friction and determine the speed at which the second...
*October 9, 2012*

**Physics**

This doesn't give me the correct answer according to the assignment program :/
*October 9, 2012*

**Physics**

A pendulum consists of a small object hanging from the ceiling at the end of a string of negligible mass. The string has a length of 0.88 m. With the string hanging vertically, the object is given an initial velocity of 1.7 m/s parallel to the ground and swings upward on a ...
*October 9, 2012*

**Finite**

Assume that the coin is weighted so that Pr[H] = [ 1/11], and that it is flipped 9 times. The random variable X is defined as the number of heads in the 9 flips. What is E[X]?
*October 8, 2012*

**Finite**

Assume that the box contains balls numbered from 1 through 28, and that 3 are selected. A random variable X is defined as 1 times the number of odd balls selected, plus 2 times the number of even. How many different values are possible for the random variable X? I know that is...
*October 8, 2012*

**Physics**

An American bald eagle heads south at 5.5 m/s, but encounters a wind blowing from the east at 1.9 m/s. By how many degrees will she be blown o course?
*October 8, 2012*

**Chemistry**

One mole of carbon (12.0 g) in the form of crystalline graphite is burned at 25 ◦ C and 1.000 atm pressure to form CO2(g). All of the heat produced is used to heat a 4560 g bath of liquid water, originally at 25 ◦ C. What is the ﬁnal temperature of the water...
*October 7, 2012*

**Chemistry**

Given the standard heats of reaction Reaction ∆H0 M(s) + 2 X2(g) → MX4(g) −123.7 kJ/mol X2(g) → 2 X(g) +297.3 kJ/mol M(g) → M(s) −25.1 kJ/mol calculate the average bond energy for a single M- X bond
*October 7, 2012*

**Chemistry**

The standard enthalpy of formation of Mn2O3 is −962.3 kJ/mol. How much heat energy is liberated when 4.7 grams of manganese are oxidized by oxygen gas to Mn2O3 at standard state conditions? Answer in units of kJ
*October 7, 2012*

**physics**

A hot air balloon descends with an overall velocity of 4.2 m/s at an angle of 36.8⁰ below the horizontal. what is the horizontal velocity of the balloon?
*October 7, 2012*

**physics**

A cup of coffee is on a table in an airplane flying at a constant altitude and a constant velocity. The coefficient of static friction between the cup and the table is 0.18. Suddenly, the plane accelerates forward, its altitude remaining constant. What is the maximum ...
*October 3, 2012*

**physics**

A 6.01-kg box is sliding across the horizontal floor of an elevator. The coefficient of kinetic friction between the box and the floor is 0.291. Determine the kinetic frictional force that acts on the box when the elevator is (a) stationary, (b) accelerating upward with an ...
*October 3, 2012*

**Math**

Has memory chip capacity's growth been exponential? How much longer is the exponential growth likely to continue? Explain.
*October 2, 2012*

**Math**

Divide 64 bundles of newspapers into two groups so the ratio is 3 to 5.
*September 29, 2012*

**physics**

Calculate the velocity needed for an object starting at the Earth's surface to just barely reach a satellite in a geosynchronous orbit. Ignore air drag and assume the object has a speed of zero when it reaches the satellite. (The orbital radius of a satellite in a ...
*September 27, 2012*

**Science**

True or false: light travels in straight lines if the medium it travels doesn't change
*September 26, 2012*

**math**

When I am rounded to the nearest hundred, I am 3,300. The diiference between my ones and thousands digits is 1. My tens digit is the same number as my ones digit. I can be two different numbers. Who am I?
*September 26, 2012*

**math**

Tks, Ms. SUE!
*September 26, 2012*

**Chemistry**

Thank you for answering this below Dr Bob
*September 26, 2012*

**Chemistry **

What volume of 0.200M of aqueous solution of formic acid, a weak monoprotic acid (KA = 1.78x10-4) and 0.200M aqueous solution of NaOH would you mix to prepare a 500mL of a buffer solution of pH = 4.0. I know I need to use the H-H equation, I'm just not sure what I plug in ...
*September 26, 2012*

**chemistry**

q= 4.184(42.3)(10.2-21.9) = -2070.70 J -2070.70J/6.60g KCl = -313.74 J/g -313.74 J/g(74.55g/ 1 mol KCl)= -23389.32J/mol -23.4 kJ/mol Is this correct?
*September 26, 2012*

**chemistry**

KCl(s) → K+(aq) + Cl‾ (aq) Solid KCl dissolves as shown in the above equation. A 6.60 g sample of KCl was dissolved in 42.3 g of water. The initial temperature of the water was 21.90°C. After the compound dissolved, the temperature of the water was 10.20°C...
*September 26, 2012*

**Chemistry **

What volume of 0.200M of aqueous solution of formic acid, a weak monoprotic acid (KA = 1.78x10-4) and 0.200M aqueous solution of NaOH would you mix to prepare a 500mL of a buffer solution of pH = 4.0.
*September 26, 2012*

**algebra**

solve the linear system from problem 1 using elimination 4x-y=5 4x+4y=-4
*September 25, 2012*

**Physics**

A plane drops hamper of medical supplies from a height of 2740m during a practice run over the ocean. The plane's horizontal velocity was 126m/s at the instant the hamper was dropped. What is the magnitude of the overall velocity of the hamper at the instant it strikes the...
*September 24, 2012*

**Physics**

A person is standing on a spring bathroom scale on the ﬂoor of an elevator which is moving up and slowing down at the rate of 2.73 m/s^2. The acceleration of gravity is 9.8 m/s^2. If the person’s mass is 75.2 kg, what does the scale read? Answer in units of n
*September 24, 2012*

**Physics**

a 96.4kg boxer has his first match in the canal zone with gravitational acceleration 9.782m/s^2 and his second match at the north pole with gravitational acceleration 9.832m/s^2. What is his mass in the canal zone? answer in units of kg
*September 24, 2012*

**Physics**

A boat moves through the water with two forces acting on it. One is a 2304N forward push by the motor on the propeller, and the other is a 2154N resistive force due to the water around the bow. What is the acceleration of the 1293kg boat? Answer in units of m/s^2.
*September 24, 2012*

**Physics**

A large uniform chain is hanging from the ceiling, supporting a block of mass 48kg. The mass of the chain itself is 15 kg, and the length of the chain is 2.6 m. The acceleration of gravity is 9.81 m/s^2 Find the tension in the chain at the point where the chain is supporting ...
*September 24, 2012*

**Physics**

When a 117 N bag of nails hangs motionless from a single vertical strand of rope, how much tension is exerted in the strand? Answer in units of N
*September 24, 2012*

**Physics**

The tension in a string from which a 6 kg object is suspended in an elevator is equal to 61 N. What is magnitude of the acceleration a of the elevator? The acceleration of gravity is 9.8 m/s^2. Answer in units of m/s^2
*September 24, 2012*

**Physics**

A person weighing 0.6 kN rides in an elevator that has a downward acceleration of 2.3 m/s^2. The acceleration of gravity is 9.8 m/s^2. What is the magnitude of the force of the elevator ﬂoor on the person? Answer in units of kN
*September 24, 2012*

**math**

I got 1:633,600 Is that correct?
*September 22, 2012*

**math**

Find the scale ratio of this map: 1 inch on the map represents 10 miles
*September 22, 2012*

**instrumental analysis**

How long would it take to discharge a 0.026 microFarad capacitor to 6.4 % of its full charge through a resistance of 1.7 MOhm?
*September 21, 2012*

**Math**

Thanks!
*September 20, 2012*

**Math**

How many liters of oil are required to supply the electrical energy needs of an average home for a month? Energy released by burning 1 liter of oil= 1.2 x 10(7th power) Electrical energy used in an average home daily 5 X 10 (7th power) I got 125 liters. Is that correct?
*September 20, 2012*

**Math**

Thanks! I have the same reasoning.
*September 20, 2012*

**Math**

Can you help me with this question? Could a person walk across the United States (New York to California) in a year? If not, about how long will it take? Explain your reasoning.
*September 20, 2012*

**Math**

Thank you! That helped.
*September 20, 2012*

**Math**

How did you get .253m? Wouldn't you multiply by 100?
*September 20, 2012*

**Math**

Can You help me with this question? The distance from the earth to the sun is about 1.5 X 10^8 km, while the distance from the earth to the moon is about 3.8 X 10^5 km. If a scale model of the solar system is constructed so that the distance from the Earth to the Sun is 100 ...
*September 20, 2012*

**Math**

What is the integral: 1/root(2x-x^2)
*September 20, 2012*

**Maths**

What is the integral of: 1/root(2x-x2)
*September 20, 2012*

**Maths**

*This is not an answer* Thanks Steve that really helps!!! *This is not an answer*
*September 19, 2012*

**Maths**

Integral of 1/root(2x-x^2)dx
*September 19, 2012*

**Chemistry**

The solubity of KNO3 at 0 is 20 g and CuSO4.5H2O at 0 is 10 g. i'm lost as to how this pertains to the answers.
*September 18, 2012*

**Chemistry**

2) To the solution in problem 1 (d) at 100 degrees celsius, 10g of water are added, and the solution is cooled to 0 degrees celsius... (problem 1d: the number of grams of water required to dissolve a mixture containing 15 g KNO3 and 3.5 g CuSO4 * 5 H20, assuming that the ...
*September 18, 2012*

**literature**

someone took away children before they were grown and they cried because they were being taken away
*September 18, 2012*

**probability and statistics**

A 0.1μm diameter drop of 1mM protein solution is introduced into pure water centered at x. Assume proteins diffuse randomly by “stepping” a distance 0.1μm every millisecond. a. What is the density at x after 1 minute? b. How many protein molecules are there...
*September 18, 2012*

**geometry**

Y is a point on HR with HO=(19x) miles and OR=48 miles. If HR=(27x) miles, find HO (in miles)
*September 16, 2012*

**Physics**

While warming up in her tryout as a pitcher for the Montwood softball team, Anabel Parga throws a softball horizontally with a speed of 22m/s. a. If home plate is 19m away, how far should the softball fall from its initial straight-line path on its way to home plate? b. The ...
*September 16, 2012*

**math**

how many combination of coins make 2.00 when given 2 quarters, 5 dimes and 18 nickels?
*September 15, 2012*

**physics**

An automobile accelerates from rest at 1.3m/s^2 for 19s. The speed is then held constant for 23s, after which there is an acceleration of -0.9m/s^2 until the automobile stops. What total distance was traveled? Answer in units of km.
*September 14, 2012*

**Physics**

Highway safety engineers build soft barriers so that cars hitting them will slow down at a soft rate. A person wearing a safety belt can withstand an acceleration of 300m/s^2. How thick should barriers be to safely stop a car that hits the barriers at 92.8km/h? Answer in units...
*September 14, 2012*

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